Process for obtaining a pepper extract with insecticidal activity

ABSTRACT

An insecticidally active fraction is obtained from black pepper by a process comprising the following steps: 
     (a) extraction of black pepper in ground form with CO 2  at 30 to 70° C. and 150 to 500 bar; 
     (b) removal of sharp tasting fractions therein in a first expansion step at 25 to 35° C. and 70 to 150 bar; 
     (c) removal of an oily fraction containing the insecticidally active components as well as most of the essential oils in a second expansion step at 15 to 30° C. and 40 to 70 bar; 
     (d) removal of essential oils by steam distillation, and if desired; 
     (e) hydrogenation of the insecticidally active components.

Ordinary commercial insecticides based on synthetic chemicals to be sureare effective, but because of their synthetic origin they areincreasingly encountering objections among broad sectors of thepopulation. Therefore, natural plant constituents with insecticidalactivity are finding increasing interest. The best known example of thisis pyrethrum, from Chrysanthemum cinerariaefolium.

Recently it was also found and described that black pepper or an extractof this shows toxic activity against a large number of insects. At firstit was suggested that the sharp tasting principle of pepper, piperine ora derivative of piperine, should be considered responsible for theinsecticidal activity. In later studies, however, it was shown that itis not piperine but rather other alkaloids of pepper which haveinsecticidal activity [Su and Horvat, Agricult. Food Chem., Vol. 29, p.115, 1981]. The authors mentioned extracted ground black pepper withacetone and isolated alkaloids containing amide groups and havinginsecticidal activity from the extract with the aid of chromatographicmethods. Black pepper is the dried, unripe fruit of the tropical plant,Piper nigrum L. and contains about 5-10% piperine as well as other sharptasting alkaloids, 1-2.5% essential oils, and smaller amounts of otheralkaloids which are not among the sharp tasting substances.

In addition, spices such as black pepper have already had theirflavoring component removed with supercritical gas in terms oftemperature and pressure, e.g., CO₂, and the extract separated bychanging the pressure or temperature (German Preliminary PublishedApplication No. 2,127,611). Spice extracts, e.g., from black pepper, canalso be obtained by withdrawing the essential oil acting as a flavorcomponent in a first step with liquid subcritical CO₂, and removing thefractions serving as the flavor carrier in a second step withsupercritical CO₂, separating the extracts by pressure and temperaturealterations, and possibly mixing them together (European Patent No.23,680). In both cases, however, the goal of this process is notdirected toward obtaining insecticidally active extracts from blackpepper, but rather at the manufacture of scenting or flavoring materialsfor the food or cosmetic industry.

It has now been found that a non-sharp-tasting fraction bearinginsecticidal activity can be extracted from black pepper with compressedCO₂ and obtained in pure form under suitable process conditions. In thisextraction and recovery process attention is to be paid to the fact thatthe sharp tasting components, especially the piperine, are not alsoenriched or separated during the process sequence, since these can leadto mucous membrane irritations during the use of the insecticidal agentin the case of people who intentionally or unavoidably come into contactwith the agent. Such an extraction and recovery process must also beeconomical and able to be carried out in the simplest possible way.

The subject of the invention is a process for obtaining a pepper extractwith insecticidal activity, characterized by the following processsteps:

(a) extraction of black pepper in ground form with CO₂ at 30°-70° C. and150-500 bar,

(b) separation of the sharp tasting fractions in a first expansion stepat 25°-35° C. and 70-150 bar,

(c) removal of an oily fraction which contains the insecticidally activecomponents as well as most of the essential oils, in a second expansionstep at 15°-30° C. and 40-70 bar,

(d) obtaining the insecticidally active components by removing theessential oils by steam distillation.

The process can also be carried out by performing the extraction of theblack pepper corresponding to the conditions of step (b) with CO₂ at25°-35° C. and 70-150 bar and separating from this by expansion at15°-30° C. and 40-70 bar according to step (c) an oily fraction, whichis further treated according to (d). In this case the sharp tastingcomponents are left behind in the extraction residue and can be obtainedfrom this, possibly by means of a further extraction corresponding tothe conditions mentioned under (a).

In a specific embodiment of the process the insecticidally activeproduct of step (d) is hydrogenated in a further step (e). An increasein the insecticidal activity can be achieved in this way. Thehydrogenation is carried out according to processes known in and ofthemselves for the hydrogenation of C--C double bonds, preferably underpressure in the presence of metal catalysts.

Objects of the invention also include the use of processed products asinsectidal active ingredients as well as insect control agentscontaining these active ingredients.

The insecticidal active ingredients obtained in process steps (d) and(e) involve light colored, usually yellow oils, not volatile with steam,which show activity against health pests and nuisance pests such asflies, mosquitoes, roaches, crickets, silverfish, ants, earwigs, woodlice, fleas, lice and bedbugs; wasps, plant pests such as plant lice,cicadas, moth larvae, beetles and their larvae; storage and materialpests such as meal beetles, grain weevils, flat grain beetles, goldenspider beetles, bread beetles, bean beetles, grain, flour and dry fruitmoths; clothing moths, carpet beetles, fur beetles, lard beetles, anddust lice. In particular a marked synergistic activity was found incombination with pyrethrum and synthetic pyrethroids, permittingconsiderable savings in these relatively expensive materials and/orshorter killing times. The insecticidal active ingredients of theinvention are combined with pyrethrum or synthetic pyrethroids in aweight ratio of 1:0.1 to 1:50, preferably 1:0.2 to 1:10.

The oily fraction obtained in process (c) already has insecticidalproperties and can be used without further processing as an activeingredient in insect control agents. However, the activity issubstantially lower than that of the active ingredients obtainedaccording to (d) or (e). In addition the considerable fraction ofessential oils can be undesirable in terms of the specific odor or therisk of contaminations during use.

The essential oils separated by steam distillation according to (d) andthe sharp tasting components of the black pepper obtained according to(b) can be used in a known way for producing flavor or aromaconcentrates for the food industry, or for odorant compositions forcosmetic purposes and the like.

The active ingredients can be used in the customary formulations, e.g.,as solutions, emulsions, suspensions, powders, aerosols, foams, pastesor granulates. The formulations are produced in known ways, e.g., bymixing the active ingredients with extenders such as liquid solventsand/or solid carrier materials. In addition surface-active agents, thusemulsifiers and/or dispersents and/or foam-generating agents, can beused in the formulations. The use of auxiliary solvents, e.g., the useof water as an extender, is likewise possible. In addition, stickingagents, coloring agents, and in the case of aerosols, propellant gasescan be added to the formulations. Combinations with other knowninsecticides and/or synergists, especially pyrethrum or syntheticpyrethroids, as well as mixtures with fungicides, acaricides,repellants, growth regulators and plant nutrients are possible. Thecontent of the insecticidal active ingredient derived from pepper insuch formulations amounts to as much as 80%, preferably 0.02 to 50%, byweight.

EXAMPLE 1 Obtaining the Insecticidal Material

The high pressure extraction described below was performed in the unitdescribed in FIG. 1. For this purpose the extraction container E 1 wasfilled with the ground raw material, the unit purged with CO₂, and theextraction conditions established by compressing the CO₂ and bringing itto the desired temperature. The removal of the material from thesupercritical gas was performed by expansion in two pressure steps inthe two separation containers A 1 and A 2. The CO₂ was reliquefied,collected in the buffer container B 1 and recompressed to extractionconditions via the membrane piston pump. The operating mode wasdiscontinuous. The extract and the extraction residue were removed fromthe high pressure containers after the end of the extraction.

Starting Material

20 kg black pepper, origin: Lampong, ground, particle fraction 200 to400μ.

Step (a): Extraction

Pressure 300 bar, temperature 50° C., time 3 hr, CO₂ circulation 10kg/kg starting material·hr

Step (b): Separation First Expansion Step (FIG. 1, A 1)

Pressure 80 bar, temperature 35° C. 1450 g yellow, solid powder(water-free)

Step (c): Separation Second Expansion Stage (FIG. 1, A 2)

Pressure 55 bar, temperature 20° C., 760 g yellow oil (anhydrous)

The extract from the second expansion step (c) was dewatered in a flowcentrifuge, and was suitable as an insecticide without furthertreatment.

Step (d): Steam Distillation

The further purification and obtainment of the insecticidally activecomponents was accomplished by steam distillation as follows:

115 g oil from the second expansion were placed in 500 ml water andsubjected to steam distillation for 4 hr. 60.5 g yellow-green pepper oilwere removed from the distillate.

The distillation residue was digested with 1 l ether under magneticagitation, and the ether extract was separated. The ether-solubleinsecticidal components (34 g) were obtained as a golden yellow oil byevaporation.

EXAMPLE 2 Obtainment of a Hydrogenated Insecticidal Active Ingredient

An oily product was produced through steps (a)-(d) as in Example 1.

Step (e)

10 g of this oil were dissolved in 25 g methanol, mixed with 1.0 gpalladiumcarbon (10.15 wt-% Pd), and hydrogenated for 20 hr at roomtemperature under a hydrogen pressure of 50 bar. After filtration andremoval of the solvent 9.3 g of a pleasant smelling slightly yellow oilremained.

EXAMPLE 3 Testing of Insecticidal Activity

To test the insecticidal activity the substances obtained according toExample 1, process step (c) or (d), in quantities of 1.5 mg, afterdilution with acetone, were placed in Petri dishes 10 cm in diameter,and after evaporation of the solvent 10 female flies of the speciesMusca domestica were placed in the covered dishes. The experiment wasrepeated three times; the following average kill rates were obtained:

    ______________________________________                                                       Kill rate in % after . . . min:                                               15   20     30     35    45                                    ______________________________________                                        substance from proccss step (c)                                                                30     47     80   90    100                                 substance from process step (d)                                                                40     53     87   100                                       ______________________________________                                    

To test the synergistic activity, using the same method 1.5 mg ofsubstance according to process step (d) and 0.03 mg pyrethrins, aloneand in combination, were tested on resistant flies. The following valueswere obtained:

    ______________________________________                                                       Kill rate in % after . . . min:                                               25  35     40     50  120  150                                 ______________________________________                                        substance from process step (d)                                                                --    --     --   50  100  --                                pyrethrins       --    50     --   --  --   100                               pyrethrins + substance from                                                                    50    90     100  --  --   --                                process (d)                                                                   ______________________________________                                    

EXAMPLE 4 Testing of Insecticidal Activity

The substances obtained from process steps (d) and (e) of Example 2, inquantities of 0.15 mg, after dilution with acetone were placed in Petridishes 10 cm in diameter. Following evaporation of the solvent 10 femaleflies of the species Musca domestica were placed in the covered dishes.The following average kill rates were obtained after determination intriplicate:

    ______________________________________                                                       Kill rate in % after . . . min:                                               25   40     60     90   120                                    ______________________________________                                        substance from process step (d)                                                                --      3     40   67   73                                   substance from process step (e)                                                                10     33     73   93   100                                  ______________________________________                                    

To determine the synergistic activity, using the same method 0.03 mgpyrethrins alone and in combination with 0.15 mg of the substances fromprocesses (d) and (e) of Example 2 were tested. The following averagekill rates were obtained from three experiments in each case:

    ______________________________________                                                      Kill rate in % after . . . min:                                               10   20      40     90   150                                    ______________________________________                                        pyrethrins      --     --      73    80  87                                   pyrethrins + substance from                                                                   --     --      90   100  --                                   process step (d)                                                              pyrethrins + substance from                                                                   50     100     --   --   --                                   process step (e)                                                              ______________________________________                                    

We claim:
 1. A process for preparing a pepper extract havinginsecticidal activity comprising the steps of:(a) extracting blackpepper in ground form with CO₂ at a temperature in the range of 30° to70° C. and a pressure in the range of 150 to 500 bar; (b) removing sharptasting fractions from the resulting extract in a first expansion stepat a temperature in the range of 25° to 35° C. and at a pressure in therange of 70 to 150 bar; (c) separating an oily fraction containing theinsecticidally active components as well as most of the essential oilspresent in the pepper in a second expansion step at a temperature in therange of 15° to 30° C. and a pressure lower than the pressure in steps(b) in the range of 40 to 70 bar; (d) removing the essential oils fromthe insecticidally active components in the oily fraction by steamdistillation.
 2. A process according to claim 1 wherein theinsecticidally active components obtained in step (d) are hydrogenated.3. A process according to claim 2 wherein the hydrogenation is carriedout under pressure in the presence of a metal hydrogenation catalyst. 4.A process for preparing a pepper extract having insecticidal activitycomprising the steps of:(a) extracting black pepper in ground form withCO₂ at a temperature in the range of 25° to 35° C. and a pressure in therange of 70 to 150 bar; (b) isolating an oily fraction from theresulting extract by an expansion step at a temperature in the range of15° to 30° C. and a pressure in the range of 40 to 70 bar; (c) removingessential oils from the oily fraction by steam distillation to produce aresidue containing sharp tasting fractions and insecticidally activecomponents; and (d) separating the sharp tasting fractions from theinsecticidally active components in the residue.
 5. The insecticidallyactive components of black pepper produced by the process of claim
 1. 6.The insecticidally active components of black pepper produced by theprocess of claim
 4. 7. A composition for insect control comprising theinsecticidally active components of claim 5 and pyrethrum or a syntheticpyrethroid in a weight ratio of from 50:1 to 1:50.
 8. A composition forinsect control comprising the insecticidally active components of claim6 and pyrethrum or a synthetic pyrethroid in a weight ratio of from 50:1to 1:50.
 9. A composition according to claim 7 wherein the weight ratiois from 50:1 to 1:10.
 10. A composition according to claim 8 wherein theweight ratio is from 50:1 to 1:10.
 11. A composition according to claim7 wherein the weight ratio is 5:1.
 12. A composition according to claim8 wherein the weight ratio is 5:1.
 13. A method for controlling insectscomprising contacting insects with the insecticidally active substancesof claim
 5. 14. A method for controlling insects comprising contactinginsects with the insecticidally active substances of claim
 6. 15. Amethod for controlling insects comprising contacting insects with thecomposition of claim
 7. 16. A method for controlling insects comprisingcontacting insects with the composition of claim 8.